The grotesque-looking Nanny McPhee (Thompson) appears at the door of harried mom Isabel Green (Gyllenhaal) who's trying to run the family farm while her husband is away at war. However, Nanny discovers the Green children have their own war going on with their spoiled city cousins who have moved in because of the London Blitz. Nanny doesn't tolerate ill-mannered behavior and proceeds to teach the children five meaningful lessons (which parents will appreciate).